Consider more semantic tags for past tenses

We currently use `` and `` in conjunction with presense or absense of `` for various past tense combinations in Turkic and Mongolic languages.

Linguistically, the system is more like this in e.g., Kyrgyz (with the same breakdown but different morpheme values in Kazakh and Khalkha):

confirmative
0+-
+recent—¹-DI-(I)птIр
-recent-GAн—¹-GAн экен

¹ -GAн is used where — is listed

A language like Turkish or Tatar has a "flatter" (less two-dimensional) system, with confirmativity and recentness conflated (or recentness ignored altogether). Basing our tags on something like this understanding would result in more linguistically valid transfer rules.

An example of how this might work is:
* -GAн:``
* -GAн экен:``(``?)``
* -DI:``
* -(I)птIр:``